Training zone, 5a, 5b, 5c vs 5 & Coggan's 6 power zones to 5

Hello, I had some hopefully simple questions that I would just like to clarify to try and ensure I am setting my training zones as accurately as possible.
I am trying to use field tests to get my lactate threshold HR’s for running and biking (vs doing the more costly lab tests that I probably won’t want to do on an ongoing basis, again due to cost).
So I am following the Joe Friel method for estimating LCTHR.
My questions are:

  • I use a polar watch that only allows for 5 zones to be input for HR (1, 2, 3, 4, & 5), Pace, and Power, however, for HR Joe Friel breaks zone 5 into a, b, and c. So, when inputting my zones into Polar do I just use the start of zone 5a as my bottom end of zone 5 and everything above that is inclusive of 5b and 5c?
  • For bike power Andy Coggan creates a 6 zone system from your FTP, however, again, Polar only allows for 5 zones. How are people adapting Coggan’s 6 zones to the more simplified 5 zone system?

I hope that makes sense.
Thank you for any confirmation and assistance.

5 zones is plenty for HR. I’m guessing 5a, b & c is covering the lower to higher end of the zones but from a performance point of view it doesn’t matter as zone 5 is hard, end of.
Don’t worry about zone 6 as your HR won’t raise in time for the effort and this can apply to zone 5 depending on duration. So, if you’re performing a zone 6 effort, just smash it out, flat out and hang on and don’t worry what your HR is doing.

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Heart rate zones really don’t matter that much once you get above threshold because of lag. The idea that heart rate can tell you whether you’re in zone 5a 5b or 5c is completely unrealistic.

The only thing I use HR for above threshold is as a percentage of maximum, as a warning for when I’m going too hard and I’m about to blow.


Having just read through Your Best Triathlon again, while he lists HR ranges for the higher zones he really recommends using bike power and run pace for the hard stuff since it’s usually shorter and there’s way too much HR lag to keep things on target properly. So like the other comments I wouldn’t worry too much about breaking it up into the 3-sub zones if your watch can’t deal with that - - I’m not sure many could and it’s probably reserved for things like WKO to delve into that level of detail?

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